Interpretive Summary: The social and emotional burdens of ostracism are well-known, but few studies have tested whether ostracism adversely alters physical activity behaviors that may result in maintenance of childhood obesity. This is the first study to experimentally assess the effect of simulated ostracism, or social exclusion, on physical activity behavior in children. Ostracism reduced accelerometer counts by 22% and increased time allocated to sedentary behaviors by 41%.

Technical Abstract:
Objective: Assess the effects of simulated ostracism on children’s physical activity behavior, time allocated to sedentary behavior, and liking of physical activity.
Methods: Nineteen (N=11 males, 8 females) children (11.7±1.3 years) completed two experimental sessions. During each session children played a virtual ball-toss computer game (Cyberball). In one session, children played Cyberball and experienced ostracism, in the other session they were exposed to the inclusion/control condition. The order of conditions was randomized. After playing Cyberball, children were taken to a gymnasium where they had free-choice access to physical and sedentary activities for 30-minutes. Children could participate in the activities, in any pattern they chose, for the entire period. Physical activity during the free-choice period was assessed via accelerometery and sedentary time via observation. Finally, children reported their liking for the activity session via a visual analog scale.
Results: Children accumulated 22% fewer (p<0.01) accelerometer counts and 41% more (p<0.04) minutes of sedentary activity in the ostracized condition (8.9e+4 ± 4.5e+4 counts, 11.1 ± 9.3 minutes) relative to the included condition (10.8e+4 ± 4.7e+4 counts, 7.9 ± 7.9 minutes). Liking (8.8 ± 1.5 cm included, 8.1 ± 1.9 cm ostracized) of the activity sessions was not significantly different (p>0.10) between conditions.
Conclusion: Simulated ostracism elicits decreased subsequent physical activity participation in children. Ostracism may contribute to children’s lack of physical activity.